本文整理汇总了C++中QgsVectorDataProvider::rewind方法的典型用法代码示例。如果您正苦于以下问题：C++ QgsVectorDataProvider::rewind方法的具体用法？C++ QgsVectorDataProvider::rewind怎么用？C++ QgsVectorDataProvider::rewind使用的例子？那么, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类QgsVectorDataProvider的用法示例。
在下文中一共展示了QgsVectorDataProvider::rewind方法的1个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的C++代码示例。
示例1: calculateStatistics
int QgsZonalStatistics::calculateStatistics( QProgressDialog* p )
{
if ( !mPolygonLayer || mPolygonLayer->geometryType() != QGis::Polygon )
{
return 1;
}
QgsVectorDataProvider* vectorProvider = mPolygonLayer->dataProvider();
if ( !vectorProvider )
{
return 2;
}
//open the raster layer and the raster band
GDALAllRegister();
GDALDatasetH inputDataset = GDALOpen( mRasterFilePath.toLocal8Bit().data(), GA_ReadOnly );
if ( inputDataset == NULL )
{
return 3;
}
if ( GDALGetRasterCount( inputDataset ) < ( mRasterBand - 1 ) )
{
GDALClose( inputDataset );
return 4;
}
GDALRasterBandH rasterBand = GDALGetRasterBand( inputDataset, mRasterBand );
if ( rasterBand == NULL )
{
GDALClose( inputDataset );
return 5;
}
mInputNodataValue = GDALGetRasterNoDataValue( rasterBand, NULL );
//get geometry info about raster layer
int nCellsX = GDALGetRasterXSize( inputDataset );
int nCellsY = GDALGetRasterYSize( inputDataset );
double geoTransform[6];
if ( GDALGetGeoTransform( inputDataset, geoTransform ) != CE_None )
{
GDALClose( inputDataset );
return 6;
}
double cellsizeX = geoTransform[1];
if ( cellsizeX < 0 )
{
cellsizeX = -cellsizeX;
}
double cellsizeY = geoTransform[5];
if ( cellsizeY < 0 )
{
cellsizeY = -cellsizeY;
}
QgsRectangle rasterBBox( geoTransform[0], geoTransform[3] - ( nCellsY * cellsizeY ), geoTransform[0] + ( nCellsX * cellsizeX ), geoTransform[3] );
//add the new count, sum, mean fields to the provider
QList<QgsField> newFieldList;
QgsField countField( mAttributePrefix + "count", QVariant::Double );
QgsField sumField( mAttributePrefix + "sum", QVariant::Double );
QgsField meanField( mAttributePrefix + "mean", QVariant::Double );
newFieldList.push_back( countField );
newFieldList.push_back( sumField );
newFieldList.push_back( meanField );
if ( !vectorProvider->addAttributes( newFieldList ) )
{
return 7;
}
//index of the new fields
int countIndex = vectorProvider->fieldNameIndex( mAttributePrefix + "count" );
int sumIndex = vectorProvider->fieldNameIndex( mAttributePrefix + "sum" );
int meanIndex = vectorProvider->fieldNameIndex( mAttributePrefix + "mean" );
if ( countIndex == -1 || sumIndex == -1 || meanIndex == -1 )
{
return 8;
}
//progress dialog
long featureCount = vectorProvider->featureCount();
if ( p )
{
p->setMaximum( featureCount );
}
//iterate over each polygon
vectorProvider->select( QgsAttributeList(), QgsRectangle(), true, false );
vectorProvider->rewind();
QgsFeature f;
double count = 0;
double sum = 0;
double mean = 0;
int featureCounter = 0;
while ( vectorProvider->nextFeature( f ) )
{
qWarning( "%d", featureCounter );
if ( p )
//.........这里部分代码省略.........